"can't compress and can't expand" you're contradicting yourself, because "can't compress" means there's no force which can compress it, and "can't expand" means there exists such a force. therefore the answer is: paradox
ok, back to sciency questions: is there a string that equals it's own md5?
Edit-jacob1: no idea, but I looked it up and it says here that there is a .632 chance that at least 1 exists ouf of all possible md5's (we just haven't found it)